1. Field of the Invention
This invention relates to a centrifuge having an interchangeable rotor provided with an information support device for storing machine-readable information, and a reader comprising detectors for scanning the information support device, and an electronic circuit for processing the received information.
2. Description
Centrifuges are generally used for separating sample particles in a liquid medium. Various different kinds of rotors are available depending upon requirements, e.g. fixed angle rotors, swinging bucket rotors, vertical rotors, and zonal rotors.
The various rotors also differ in respect of performance, e.g. maximum attainable centrifugal force and maximum usable volume.
Since centrifuges are frequently used not just for one application, various interchangeable rotors are used for one and the same centrifuge. In no case may the maximum speed of the rotor used by exceeded.
Modern centrifuges, therefore, usually have a corresponding rotor-specific means of preventing excessive speed, e.g. optical scanning of a light/dark disc by an opto-coupler or similar methods or magnetic monitoring of a toothed disc or permanent magnets.
Both methods are adapted to generate a frequency which switches off the centrifuge drive if the permissible value is exceeded. In the case of centrifuges without vacuum facilities, the above mentioned monitoring is frequently eliminated. Protection against excess speed is provided by the air resistance.
High-speed centrifuges usually have cooling in order to keep the sample temperature inside the rotor constant. This type of centrifuge has no vacuum facilities of the kind required in even higher-speed ultracentrifuges.
The air resistance depending on the size, shape, surface and speed of the rotor used must be taken into account in the temperature control. This means that the cooling capacity must be appropriate for the purpose. This is achieved by a compensation circuit. The correct compensation value can be derived from the corresponding nomograms of the individual rotors.
In the case of centrifuges equipped with microprocessors it is only necessary to preselect the rotor type in order automatically to allow for compensation in connection with preselection of the temperature from the microprocessor memory. The same applies to partially evacuated centrifuges.
Many rotors, and particularly in the case of ultracentrifuges, are heavy-duty rotors, the use of which is limited by the total number of runs or running times or age. This necessitates keeping records of each run. Safety regulations in different countries expressly require this. Modern centrifuges have a printer which keeps a record of the runs provided the correct rotor type has previously been manually input.
The disadvantage of the technical solutions for keeping records is that the rotors are not automatically identified by the centrifuge. As a result, an error on the part of the user may make faulty operation possible so that inaccurate rotor records are retained. Rotors of excessive age are not recognized as such, and a sample in the rotor may not be kept at the required value due to false compensation of the centrifuge temperature control system.